First, I agree with Purple in that I'd be weary of playing in a league like this where the commissioner doesn't involve the other teams prior to implementing significant rule changes. Also, I'm hoping that this isn't any type of keeper league where teams already have players and I'm also hoping that the draft order wasn't set before the commissioner made these changes. If it was not a 100% fresh start to a new season when the changes happened, I would look to get out quickly.
With all that said, I only think this pushes the value of RBs relative to other positions up slightly. At the end of the day, the RBs will score the same as they did last year for the most part and the WRs will score a little less. Depending on where you are drafting, I would look to secure 2 of the top 15 WRs if possible and then fill in my RB core with a couple of riskier RB picks coming from rounds 4 through 7. For example and assuming you have a late 1st round pick. I would look to grab something like this (but be aware that every draft is unique and you need to go with the flow of the draft):
1st Round - RB
2nd Round - WR
3rd Round - WR if a top 15 WR falls, if not RB
4th Round - The opposite of Round 3
5th Round - Grab a TE if one of the big 4 are left.
6th Round - Grab another RB here.
7th Round - Grab another RB here.
So, assuming this works the way I think it will, you will end up with a 1st round RB, at least 1 top 3 WR, either a top 15 or at worst a top 20 WR, 3 RBs to platoon as your RB2, and a top 4 TE. Then pick 2 QBs later in the draft to platoon all season long and you will have a competitive team if you drafted the right guys.
My Playoff Team - Please Comment
MSchaub, DMcNabb, JFreeman, KKolb
SJackson, THightower, CWells, JForsett, JSnelling, CJennings, QGanther
RWayne, RMoss, RMeachem, MCrabtree, DBowe